“Crimp” is a term that is used to describe the waviness or nonlinearity of yarns in woven fabrics. Typically, such yarns have an “over and under” shape caused by weaving. The more crimp that is present in a woven fabric, the more the fabric will stretch. Stretchiness is an important consideration in the selection of a woven fabric as sailcloth. If sailcloth stretches too much, it loses it shape and is aerodynamically inefficient.
The sail-making industry has attempted to address the issue of crimp in a number of ways. For example, sailcloths have been laminated with one or more layers of nonwoven plastic film to minimize stretching of the sailcloth in the wind. Unfortunately, laminated sailcloths delaminate with age, use, and exposure to the elements. In addition, the laminating film tends to crease and shrink with use, thereby adversely affecting the shape of the sail.
Also in an effort to minimize stretching, sailcloth, which has been tightly woven from polyester yarns, has been impregnated with a resin and heated to cure the resin and shrink the polyester fabric. In order to construct sails from this cloth, numerous panels must be assembled to align the yarns will less crimp along directions of maximum stress or load in the sail so as to reduce stretch. Therefore, the disadvantage of this type of sailcloth is that it limits how panels can be cut and arranged in a sail, while still using the cloth efficiently.
Sailcloth also has been constructed with a reinforcing yarn to minimize stretching. The reinforcing yarn, which has a higher tensile modulus (e.g., above 500 grams/denier) than conventional yarn (tensile modulus of 20-100 grams/denier for Dacron or polyester), has been used to replace the conventional yarn every so many yarns in the warp and/or fill direction, while maintaining the denier (see, e.g., Bainbridge et al., U.S. Pat. No. 5,304,414). More recently, sailcloths have been woven from heat-shrinkable yarn with crimp imparted to the fill yarns, while leaving the warp yarns relatively uncrimped and while maintaining a high yarn density. The sailcloth is woven with more space between the warp yarns than conventional fabrics and a fill vs. warp weight ratio of between 1.0 to 1 and 0.22 to 1 (see, e.g., Mahr, U.S. Pat. No. 6,725,885).
More structured sails have been developed for racing. Fabric strips, which contain bundles of monofilaments, have been taped onto the skin or membrane of the sail along the load path in the sail. However, such sails have proved to have insufficient strength. Consequently, structural sails having a complex secondary structure in which the angles of warp yarns with respect to fill yarns vary in one panel relative to another panel have been proposed (see, e.g., Keire, U.S. Pat. No. 6,257,160). Separately, the use of pre-crimped fill yarn has been proposed to allow for warp yarn to remain predominantly straight with very little crimp (see, e.g., Cronburg, U.S. Pat. App. Pub. No. 2006/0157138).
In view of the above, the present disclosure seeks to provide a method of reducing crimp in woven sailcloth that provides fabric with straighter warp or fill yarns, yet is simple and easy to use. This and other objects and advantages, as well as inventive features, will become apparent from the detailed description provided herein.